Colour inorganic led display for display devices with a high number of pixel

ABSTRACT

An image generator for use in a display device, the image generator comprising a plurality of ILED array chips each comprising a plurality of ILED emitters and arranged in an array such that each of a plurality of pixels of the image generator comprises an ILED emitter from each of a plurality of adjacent ILED array chips. The total area of ILED emitter material be less than 50% of the area of each pixel. The image generator may comprise secondary optics in optical communication with an output of the plurality of ILED emitters of an ILED array chip and configured to direct light from the ILED emitters towards an emission region of the associated pixel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/269,505, filed Feb. 6, 2019, which is a continuation of U.S.application Ser. No. 15/329,554, filed Jan. 26, 2017, now U.S. Pat. No.10,262,977, which is a National Phase Application of InternationalApplication No. PCT/EP2015/067751, filed Jul. 31, 2015, which claims thebenefit of United Kingdom Application No. 1413604.8, filed Jul. 31,2014, each incorporated by reference in its entirety.

TECHNICAL FIELD

The invention relates to an image generator. Specifically, the inventionrelates to, but is not limited to, an image generator that efficientlyuses light and ILED real estate leading to enhanced power efficiency inlarge area/higher resolution displays while solving manufacturabilityissues and achieving a cost that is competitive with other displaytypes.

BACKGROUND

The current state of the art comprises of the arrangement of R, G and Bdisplay subpixels to form a single display pixel. A typicalconfiguration for a low resolution display is highlighted in FIG. 1,where discrete R, G and B ILED chips are packed together to provide thenecessary light for each pixel of the display. In this example, each R,G and B chip has one emitter per chip. The typical/minimum size of theseR, G, B chips is 50 μηt×50 μηt. For larger displays with moderateresolution the one to one relationship between ILED chips and displaysub pixel results in the requirement for a very large number of ILEDchips. This raises significant manufacturability and cost challenges.For ultra-high resolution displays the size of the ILED chips limits thearea and size of the pixel display and thus the overall displayresolution. In this instance, the display pixel size is limited to 100μηt×100 μηt area which is not sufficient to achieve a high resolutiondisplay sub 20 μηt×20 μηt in area.

An alternative approach may be to reduce the size of ILED chips. It istechnically complicated and challenging to manufacture and place chipsthat are smaller than 20×20 μηt on a substrate or driver backplane,which therefore limits the display pixel size (albeit at a low level).In addition this does not address the issue of the number of placementsteps required. This would therefore remain technically and financiallychallenging.

SUMMARY

According to an aspect of the invention, there is provided an imagegenerator for use in a display device, the image generator comprising: aplurality of I LED array chips each comprising a plurality of ILEDemitters and arranged in an array such that each of a plurality ofpixels of the image generator comprises an ILED emitter from each of aplurality of adjacent ILED array chips, and wherein the total area ofILED emitter material is less than 50% of the area of each pixel.

Optionally, the total area of ILED emitter material is in a range from5% to 10% of the area of each pixel.

Optionally, the image generator further comprising secondary optics inoptical communication with an output of the plurality of ILED emittersof an ILED array chip and configured to direct light from the ILEDemitters towards an emission region of the associated pixel.

Optionally, the secondary optics comprise one or more of: reflectivestructures, light turning optics, light extraction features, Fresneltype structures, printed optics, etched optics, holographic optics,diffraction grating or other type of optical component.

Optionally, the light extraction features are configured to reduce orremove internal reflection of the secondary optics, such that light isemitted from the secondary optics.

Optionally, the size and/or shape of the pixel emission region isdetermined by the size and shape of the light extraction features.

Optionally, the image generator further comprising a diffuse light guidepanel at the output.

Optionally, the diffuse light guide panel comprises an interpixel regiondefining each pixel of the display device and configured to preventinterpixel cross talk.

Optionally, the interpixel region comprises a gap.

Optionally, the gap is at least partially filled with one or more of adielectric material and a reflective material.

Optionally, each ILED chip has a monolithic structure.

Optionally, the plurality of ILED emitters on each ILED array chip areconfigured to emit light of substantially the same colour.

Optionally, the colour is one of red, green and blue.

Optionally, the plurality of ILED emitters on each ILED array chip areconfigured in a 2×2 matrix.

Optionally, the ILED array chips are one of square, rectangular,triangular, circular and polygonal in shape.

Optionally, each of the plurality of ILED emitters on each ILED arraychip are mounted at a corner of the ILED array chip.

Optionally, the ILED emitters are mounted on a substantially transparentcarrier such that the emitted light propagates through the carrier.

Optionally, the secondary optics are directly integrated with the ILEDarray chip.

Optionally, the secondary optics are directly integrated with the lightguide panels.

Optionally, the ILED emitters comprise micro ILED emitters.

According to an aspect of the invention, there is provided an imagegenerator for use in a display device comprising: a plurality of ILEDarray chips each comprising a plurality of ILED emitters and arranged inan array such that each of a plurality of pixels of the display devicecomprises a ILED emitter from each of a plurality of adjacent ILED arraychips; and secondary optics in optical communication with an output ofthe plurality of ILED emitters of a ILED array chip and configured todirect light from the ILED emitters towards an emission region of theassociated pixel.

Optionally, the secondary optics comprise one or more of: reflectivestructures, light turning optics, light extraction features, Fresneltype structures, printed optics, etched optics, holographic optics,diffraction grating or other type of optical component.

Optionally, the light extraction features are configured to reduce orremove internal reflection of the secondary optics, such that light isemitted from the secondary optics.

Optionally, the size and/or shape of the pixel emission region isdetermined by the size and shape of the light extraction features.

Optionally, the image generator further comprising a diffuse light guidepanel at the output.

Optionally, the diffuse light guide panel comprises an interpixel regiondefining each pixel of the display device and configured to preventinterpixel cross talk.

Optionally, the interpixel region comprises a gap.

Optionally, the gap is at least partially filled with one or more of adielectric material and a reflective material.

Optionally, the ILED emitters are mounted on or embedded into asubstantially transparent carrier such that the emitted light propagatesthrough the carrier.

Optionally, the secondary optics are directly integrated with the ILEDchip.

Optionally, the secondary optics are mounted on or embedded into thelight guide panels.

Optionally, the ILED emitters comprise micro ILED emitters.

According to an aspect of the invention, there is provided a displaydevice comprising an image generator according to any preceding claim.

This invention aims to mitigate or solve one or more of the problemswith the prior art. The invention greatly reduces the issues associatedwith cost, manufacturability and minimum pixel size.

According to the invention in a first aspect, there is provided adisplay device comprising: a plurality of ILED chips each comprising aplurality of LED devices and arranged in an array such that each of aplurality of pixels of the display device comprises one or more LEDdevices from a plurality of adjacent I LED chips.

Optionally, the LED devices comprise one or more LED devices.

Optionally, the display device further comprises secondary optics inoptical communication with an output of the plurality of LED devices ofan I LED chip and configured to direct light from an LED device towardsthe associated pixel.

Optionally, the secondary optics may be directional optics to manipulateand control the light path direction from the I LED chip to and withinand from the light guide panel. The secondary optics can comprise one ormore of: reflective structures, light turning optics, backreflectors,light extraction features, Fresnel type structure, printed optics,etched optics, holographic optics, diffraction grating optics or othertype of optical component.

Optionally, the display device further comprises a diffuse light guidepanel at the output, wherein the diffuse optical layer comprises aninterpixel region defining each pixel of the display and configured toprevent interpixel cross talk.

Optionally, the interpixel region comprises a gap.

Optionally, the gap is at least partially filled with one or more of adielectric material and a reflective material.

Optionally, each I LED chip has a monolithic structure.

Optionally, the plurality of LED devices on each ILED chip areconfigured to emit light of substantially the same colour.

Optionally, the colour is one of red, green and blue.

Optionally, the plurality of LED devices on each ILED chip areconfigured in a 2×2 matrix.

Optionally, the ILED chips are one of square, rectangular, triangular,circular and polygonal in shape.

Optionally, the plurality of LED devices on each ILED chip define one ofa square, a rectangle, a triangle, a circle and a polygon.

Optionally, the ILED devices are mounted on a substantially transparentcarrier such that the emitted light propagates through the carrier.

Optionally, the secondary optics are directly integrated with the ILEDchip.

Optionally, the secondary optics are directly integrated with the lightguide panels.

Optionally the ILED chips are embedded into the light guide panels withintegrated secondary optics.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are discussed herein withreference to the accompanying drawings, in which:

FIG. 1 is basic side view of standard ILED type display for lowerresolution applications and smaller screen sizes;

FIG. 2A is a low resolution pixel display—the typical pixel display sizeis 100 μm×100 μm;

FIG. 2B is an exemplary display in which each display pixel isilluminated by 3 ILED chips (R, G and B). Typical chips size is 50 μm×50μm;

FIG. 3 shows a schematic representation of a micro I LED emitter;

FIG. 4 is a simplified side view of an I LED display for high resolutionand large area displays where the light from neighboring ILED devices isshared amongst display pixels;

FIG. 5A is an image of the use of secondary optics to spatially directthe light emitted from LED emitters on the same ILED chip;

FIG. 5B is an expanded image of the use of secondary optics to spatiallyposition light from one LED emitter on the same I LED chip.

FIG. 6A is a Light Guide Panel as an example of secondary optics;

FIG. 6B is a light guide panel integrated with ILED chips for H Ddisplay solution. In this example, the Display pixel size is 20 μm×20μm. The ILED chip size is equivalent in area to the display pixel sizeand has 4 subpixels which are 5 μm×5 μm in area;

FIG. 6C is a cross section through two neighboring pixels A and Bhighlighting interpixel gap and light directing structures by way ofexample to steer and control the light in the display emission area;

FIG. 7 is an example of pixel layout with a larger pixel size. Note thatthe ILED chip size does not need to increase to accommodate the largedisplay pixel size. This enables the fabrication of displays ofincreased size without the need to increase the amount of wafer materialor chip interconnects required; and

FIG. 8 is an example of a hexagon I LED chip with 6 I LED emitters. Eachof the I LED can be used to illuminate alternative display pixels.

DETAILED DESCRIPTION Overview

Disclosed herein is a novel ILED display, which may be based on the highefficiency ILEDs that may be coupled with a light guide panel and can beused for display applications with a high number of pixels, due tolarger screen sizes, high display resolution or other performancerequirements.

Specific exemplary devices and methods, relate to an inorganic lightemitting diode (ILED) image generator with a high number of pixels,having improved power efficiency. The requirement for a high number ofpixels may be due to a large screen size with a moderate resolution or asmall screen size with an ultra-high resolution.

In the case of the former this invention is applicable to portableelectronic devices such as mobile phones, tablet computers, monitors andtelevisions. In the case of the latter, exemplary devices and methodsmay also be used for small displays with ultra-high resolution where thelimiting factor is the minimum size of the light source to bemanipulated. Examples of such an application include a near-to-the-eyemicro-display such as used in thermal images or helmet mounted systemsand pico-projectors.

As used herein, the term “image generator” encompasses an array of ILED(or μILED) array chips that provide light for a plurality of pixels. TheILED array chips comprise a plurality of ILED emitters, may bemonolithic and may generate light all of a single colour. Each ILEDemitter of an ILED array chip provides light to one of adjacent pixelsof the image generator. The image generator may be considered as asingle device that provides a light source and an image engine of adisplay.

The methods and apparatus disclosed present a manufacturable solutionfor ILED displays where there are a large number of pixels. This may bedue to a large display that has a moderate or high resolution; or asmall display that has an ultra-high resolution (and hence a largenumber of pixels).

An exemplary display module comprises

-   -   1. A plurality of ILED array chips each of a single color (i.e.        R, G and B emission wavelengths).    -   2. Each ILED array chip comprising one or a plurality of        individual ILED emitters, where the individual ILED emitters may        form sub pixels of a display, as set out below.    -   3. Apparatus and a corresponding method for controlling the        light from the ILED emitters, such that the light is        appropriately spatially positioned to form the sub pixels of the        display.—“secondary optics”.    -   4. Display pixel emission region, which is an emission area for        light from a combination of R, G and B color ILED emitters.

In particular the invention discloses a method of manufacturing adisplay with a high number of display pixels and reducing or minimizingthe number of ILED array chips that are required in the display. Theinvention has applications for larger area (>1″ diagonal) displays andultra-high resolution displays while achieving a cost base that iscompetitive to other display types.

In exemplary methods and apparatus, the ILED emitters may be ILED(μILED) emitters, as disclosed herein.

The invention represents a simpler manufacturing solution for achievinghigh resolution displays whereby ILED array chips are manufacturedcomprising a plurality of individual sub pixels. That is, the ILED arraychips may comprise a plurality of ILED emitters and each ILED emittermay form a sub pixel on a different pixel. A sub pixel being one of aplurality of light emitting devices required to make up a pixel.Typically, sub pixels may emit light at wavelengths corresponding to oneof red, green or blue light.

This invention is related to a display type where a ILED array chip isused as the light source and image generator. It is distinct from LCDbased displays (where the light source may be an LED via a backlight)but the image generator is a liquid crystal module.

This invention overcomes this issue by manufacturing ILED chipscontaining one or a plurality of ILED emitters on a single ILED arraychip. Specifically, the invention disclosed involves the sharing oflight emission from a single ILED array chip comprising multiple subpixels with neighboring display pixels. The ILED array chip may beshaped according to the number of ILED emitters formed on it. Inexemplary methods and apparatus, each ILED emitter may be positioned ata corner or near the edge extremity of the ILED array chip. For examplea ILED array chip with 3 ILED emitters may be in the shape of atriangle. A ILED array chip with 4 ILED emitters may be square. A ILEDarray chip with 6 ILED emitters may be hexagonal. The skilled personwill understand that other corresponding configurations are possible.

Exemplary devices use light controlling structures, which may be in theILED emitter. This ensures that there is minimal cross-talk between theILED emitters that are on the same ILED array chip (i.e. crosstalkacross pixels). The light controlling structure allows the generatedlight to be directed from the ILED emitter in a quasi-collimatedfashion. This allows the light to reach secondary optics in awell-defined manner thus allowing the secondary optics to performeffectively.

FIG. 2 discloses a low resolution pixel display with the typical pixeldisplay size in this example being 100 μηt×100 μηt. FIG. 2(b) is anexemplary display in which each display pixel is illuminated by 3 ILEDchips (R, G and B). Typical chip size is 50 μηt×50 μηt. Other classicpixel matrix configurations include stripe pixel designs consisting of 3subpixels; i.e. 1 R, 1 G & 1 B and square pixel designs consisting of 4subpixels which consists of a least 1 R, 1 G and 1 B subpixel. In thisconfiguration it may also contain 1 yellow (Y) subpixel.

The ILED emitters may be ILED emitters as shown in FIG. 3, which shows aILED structure 100 similar to that proposed in WO 2004/097947 (U.S. Pat.No. 7,518,149) with a high extraction efficiency and outputtingquasi-collimated light because of its shape. Such an ILED 300 is shownin FIG. 3, wherein a substrate 302 has a semiconductor epitaxial layer304 located on it. The epitaxial layer 104 is shaped into a mesa 306. Anactive (or light emitting) layer 308 is enclosed in the mesa structure306. The mesa 306 has a truncated top, on a side opposed to a lighttransmitting or emitting face 310. The mesa 306 also has anear-parabolic shape to form a reflective enclosure for light generatedor detected within the device. The arrows 312 show how light emittedfrom the active layer 308 is reflected off the walls of the mesa 306toward the light exiting surface 310 at an angle sufficient for it toescape the LED device 300 (i.e. within the angle of total internalreflection).

The I LED array chips may positioned relative to other I LED array chipssuch that the ILED emitters are shared equally between nearest neighbordisplay pixels, as shown in FIG. 4. FIG. 4 is an image of multiple ILEDarray chips 400 a-d with the light from a single ILED array chip 400 a-dbeing emitted from adjacent pixels 402 a-d. The pixels 402 a-d maycomprise a light guide panel 403, the operation of which is discussedbelow. Each pixel 402 a-d may comprise at least one discrete light guidepanel 403, or the light guide panel 403 may be used for a plurality ofpixels 402 a-d. FIG. 5a shows a single ILED array chip 500 with thesecondary optics 502 being used to separate light from emitters 504 a-binto different pixels 506 a-b.

The ILED array chip size does not need to be small chips as they aredesigned with multiple ILED emitters which are utilized in a suitableconfiguration. In exemplary methods and apparatus, each ILED emittercontributes to an individual sub pixel of the display pixel. In thisway, each ILED array chip will contribute to multiple display pixels. Asan ILED array chip contains multiple ILED emitters the number ofplacement steps for a given number of pixels is reduced. In exemplarymethods and apparatus, the use of a common cathode for the ILED arraychips reduced the number of contacts required in a display.

An example of a suitable configuration is the following based on squareor rectangular ILED array chips which contain 4 sub pixel emitters areshown in FIG. 5(a). The integration of multiple ILED emitters per arraychip allows for the design of ultra-small display pixels. For example, a20×20 μηt chip may contain 6 ILED emitters. However, a display pixel mayrequire only 3 ILED emitters (e.g., 1 for R, G and B—albeit fromdifferent ILED array chips). Therefore with the appropriate positioningof the ILED array chips, a display smaller than the minimal ILED arraychip size could be created. This is a route to ultra-high resolutiondisplays with high efficiency.

The emission from the ILED emitters may be directed and diffused intothe appropriate spatial position to form a display pixel via a number ofmethods and apparatus. These methods are herein referred to as thesecondary optics.

One such method is a light guide panel 510 (see FIGS. 5(b) & 6). Thesecondary optics may comprise a lightguide panel 510 that is configuredto direct light emitted from a display sub pixel (i.e. an ILED emitter)towards a display pixel emission region 512. The lightguide panel 510may be configured such that the R, G & B colors can be intermixed in thepixel display emission area 512. Note that in this application the term“light guide” encompasses to a transparent or translucent material thatallows light to propagate from one point to another. In certainembodiments, this may also result in restrictions in the directionalityof the light.

As demonstrated in FIG. 5(b), the collimated light emission pattern fromthe ILED emitters 504 is directly coupled into the lightguide 510 bybutt coupling the ILED array chip 500 to the lightguide 510. This may bedone using a light index matching layer. The emitter 504 may bepositioned at a corner of the display pixel 506 a, as shown in FIG. 7.However, the light from the emitter 504 may need to be propagated to adifferent area of the pixel 506, such as the display pixel emissionregion 512. The lightguide 510 may comprise light turning reflectoroptics 514 configured to internally reflect the light rays coupled intothe lightguide 510, such that they are directed to the desired region.The light turning reflector optics 514 may be positioned substantiallyin the path of light entering the lightguide panel 510 from the emitter504 and in particular methods and apparatus may comprise a cornerreflector positioned in a corner of the lightguide panel 510. The lightturning reflector optics 514 may be configured to turn the light emittedfrom the emitter 504 by 90 degrees to reflect the light rays. Thelightguide may comprise further features, such as a backreflector layer516 configure to reflect light internally such that light rays propagatealong the lightguide 510 by a combination of total internal reflection(from an output surface 518) and the optional backside reflective mirroror features 516. Light reaching the pixel emission region 512 may thenbe extracted using light extraction features 520 which define the pixelemission region 512. The light extraction features 520 are configured todirect light out of the lightguide 510 at the pixel emission region 512and may comprise ridged features that reduce or remove the internalreflection properties of the output surface 518. The pixel size andshape may be defined by the light extraction features 520 and these canbe varied to control the shape and size of the pixel emission size. Thelight extraction features 520 can be mounted directly onto the surfaceof the lightguide 510 (as shown in FIG. 5(b)) or physically etched intothe light guide 510. The example shown shows LEDs coupled to a thin filmlightguide 510 but it is also appreciated here that the I LED arraychips can be embedded directly into the thin lightguide layers.

In exemplary methods and apparatus, the ILED array chip may be embeddedin the lightguide. In such methods and apparatus, a recess may bemachined in the secondary optics and an ILED array chip may bepositioned in the hole such that an upper surface of the ILED array chipis flush with or below the surface of the lightguide. Optionally, afilling compound may be injected into the recess to retain the ILEDarray chip in position and the external surface of the lightguide may beplanarized.

In this embodiment the light support panel or light guide panel providesfor

-   -   1. the controlled directionality of light emitted from an ILED        emitter within a pixel    -   2. the controlled separation of light emitted from ILED emitters        of a single ILED array chip between neighboring pixel displays,        i.e. the removal of interpixel crosstalk.

As such, the secondary optics (i.e. directional optics) are configuredto direct light emitted from ILED emitters of a ILED array chip alongthe light guide towards the pixel emission area. Exemplary secondaryoptics may direct light towards a central region of the pixel.

To control the light directionality, the light guide panel may consistof a series of optical components e.g. light turning optics, microlens,laser machined light structures for controlled light reflection or areflector in combination with a diffuse plate. The light guide panelconsists of light scattering structures which may direct the light fromeach ILED emitter (sub pixel) and converge it into the region ofinterest namely across the surface of the pixel, in exemplary methodsand apparatus, the secondary optics are on the side where light isinjected into the light guide. The secondary optics may be positionedbetween a light emitting face of an ILED emitter and the light guide.Additional optical components may be used at the exit face of the lightguide (which may also be the exterior face of the electronic device) tofurther control the light for various benefits.

To control the separation of light between neighboring pixels in thedisplay, the light guide panel can be machined such that it issubdivided into arrays of optically independent pixels having interpixelgaps between the optically independent pixels. The interpixel gaps canextend partially through the light guide panel or all the way throughthe light guide. This is one method of the secondary optics.

The optically independent pixels are configured to channel detectablelight to the pixel emission area thereby reducing optical crosstalkbetween the pixels and increasing light efficiency of the display, andmaintaining a high spatial resolution necessary for HD displayapplications. The interpixel gaps may be filled with a dielectric and oroptically reflective material to substantially reduce optical crosstalkand enhance light collection efficiency within the pixel. The lightpanel guide is transparent and can be machined using glass or polymerbased materials such as PMMA or PVC.

In another exemplary embodiment the secondary optics for the spatialpositioning may be provided by independent optical components. In otherexemplary embodiments, the secondary optics may be integrated with thetransparent carrier layer of the display. In another exemplaryembodiment, the optical components can be directly integrated with the ILED array chip. This may be on the opposite side from the area where thelight is generated and enters the light guide panel. The optics can bein a number of forms. The optics may be formed using reflectivestructures, Fresnel type structures, printed optics, etched optics,diffraction gratings or any other applicable method. The use of a μILEDemitter to efficiency couple the generated light to the secondary opticsimproves the efficiency performance of the display.

The quasi-collimated light produced by the ILED emitters also enablesthe secondary optics to perform in a predicable way. Thequasi-collimated light minimizes the cross-talk between the ILEDemitters on the ILED array chip and as such reduces the cross-talkbetween display pixels. The quasi-collimated light inside the ILED arraychip due to the ILED emitter structure allows the ILED emitters to beplaced closely together and hence reduces the ILED array chip size. Anexample of the control of light using optical structures is given inFIG. 4 with further detail provided in FIG. 5.

A mixture of multiple solutions may be used to control the light. Forexample, a secondary optics component may be used to direct the lighttowards the display pixel. As part of the transparent layer there may begrooves on one surface that further separate the light between pixelsand reduce cross-talk. Other components may also be included to furtherenhance the performance.

Note in FIG. 6(a) the target display pixel size is shown as 20×20μm—i.e. ultra-high resolution. For displays of lower resolution, i.e.most current mobile phones, tablets or televisions the size of displaypixel would be significantly larger. However, with the current inventionthe size or number of the ILED array chip does not need to increase withincreasing display pixel size. Therefore the fill factor within thepixel can be relatively low and the amount of material required tofabricate a larger display with a lower resolution is equivalent to thatof a small display with ultra-high resolution. Another way of explainingthis is that the total amount of ILED material and the number of ILEDarray chip placement steps required is dependent on the number of pixelsand not the size of the display. In addition, the use of the multiplesub pixels per ILED array chip reduces the number of placements andinterconnects required for a given pixel count.

The term “fill factor” as used herein encompasses the ratio of ILEDmaterial in relation to the total area of the pixel. This may also beexpressed as a percentage of the total pixel area.

FIG. 7 shows a layout for a display with a larger pixel size shown thanthat in FIG. 6. The secondary optics are removed in this diagram.Exemplary methods and apparatus may include the secondary optics, butthe quasi-collimated light emitted by the ILED emitters means that thesecondary optics are not essential. Note that the pitch between the ILEDarray chips is increased for the larger pixel size and is shown in FIG.7 as being 100 However, the number of ILED array chips and the size ofthe ILED array chips does not increase with respect to the smallerdisplay of FIG. 6. This enables a larger display to be fabricatedwithout the need for an increase in the ILED array chip area or thenumber of interconnections. This invention therefore overcomes a numberof the manufacturability and cost issues associated with the fabricationof ILED displays in larger devices.

In exemplary methods and apparatus, the fill factor of the ILED materialof the ILED array chips within the total pixel area is less than 50%. Inother exemplary methods and apparatus, the fill factor is less than 20%.In other exemplary methods and apparatus, the fill factor is less than10%. In other exemplary methods and apparatus, the fill factor is lessthan 5%. And in specific exemplary methods and apparatus, the fillfactor is in a range from 5% to 10%.

Secondary optics may be added to reduce interpixel crosstalk and/or tomix the light from a plurality of I LED emitters from adjacent ILEDarray chips.

FIG. 5 shows a simplified side view of the ILED display for higherresolution and larger displays. A single ILED array chip 500 willcontain multiple addressable sub pixel emitters 504 a-b. Each of thesesub pixels can be used to couple light to a different display pixel 506a-b. This is achieved using a secondary optics component 502 that may bemounted directly on the ILED emitter or may be on the transparentcarrier (or light guide plane) 503. In the case of FIG. 5 the secondaryoptics component 502 is mounted directly to the light guide panel 503surface on a surface that may abut the light emitting surface of theemitters 504 a-b. The use of multi-sub pixel I LED array chips reducesthe number of ILED array chips required and hence both the total area ofILED material and the number of placement steps. The limit of currentavailable pick-and-place techniques is approx. 20 μm.

In summary, exemplary embodiments of the invention may be based oneither or both of 2 components. Firstly, an ILED monolithic array (theILED array chip) is used to generate light for the display. The use of amonolithic array with multiple I LED emitters is vital as it reduces thenumber of pick and place steps and the packaging complexity. Themonolithic array is also important in that it enables the use of verysmall display sub pixels. More specifically, there is a limit on thesize of chip that can be reliably “picked-and-placed” during assembly ofapprox. 20 μm. The use of monolithic array allows for example 4 emitterpixels to be on a chip of 20×20 μm with each pixel being 5 μm. Thisresults in an efficient use of ILED material and therefore allows thecurrent invention to be cost competitive.

The monolithic array is built on the LED device structure such that thegenerated light is controlled at the chip level. This allows eachemitter in the monolithic array to efficiently illuminate its targetpixel area. Overlap and cross-talk between pixels in a monolithic arrayis a potentially significant drawback as it would result in the unwantedillumination of neighboring pixels. This would reduce the absolute blackthat could be achieved by the display and hence the contrast. Thecrosstalk may also result in losses to the target pixel area of thedisplay and hence reduce the overall efficiency. The use of collimatedILED emitters reduces the crosstalk as the light is controlled at thepoint of light generation. In order for the monolithic chip to be ableto illuminate multiple display pixels the chip may be placed at theintersection of the pixels, see FIGS. 4-7.

Exemplary methods and apparatus may additionally, or alternativelyinclude “secondary optics”. These secondary optics are used to directlight into the target pixel area (i.e. the display pixel). As aconsequence they will also serve to reduce the crosstalk between pixels.

The present applicant has identified that a ILED array chip containing a2×2 monolithic array of ILED sub pixel emitters on a single chip can beused to illuminate multiple pixels within a display. The use of thearray will reduce the total ILED array chip area relative to the size ofa pixel, the total number of placement steps and the packagingrequirements for the display. This design will allow for theconstruction of displays with high efficiency, high resolution overlarge area and/or pixel numbers while achieving a cost that iscompetitive with existing solutions.

The diagrams and discussions above describe a square chip with fourpixels. However the current invention is applicable to designs of anumber of geometries. Of particular relevance is a hexagon shaped ILEDarray chip containing 6 emitter pixels. In this embodiment eachmonolithic ILED array chip would contribute to 6 display pixels.

TABLE 1 Number of Pick-And-Place steps required for a given chip designNo of pixels Pixels per (SVGA − 800 × Pick and Total P&P Type 600)Colours Place steps Standard 480,000 3 1 1,440,000 Square 4 pixel480,000 3 4 360,000 monolithic Hexagon 6 pixel 480,000 3 6 240,000monolithic

TABLE 2 Area of LED material required for a given chip design. No ofpixels Pixels per (SVGA − 800 × Pick and Total P&P Type 600) ColoursPlace steps Standard 1,440,000 20 × 20 400 576 Square 4 pixel 360,000 20× 20 400 144 monolithic Hexagon 6 pixel 240,000 20 × 20 400 96monolithic

Exemplary embodiments of the invention may be defined by the followingnumbered clauses:

-   -   1. A method for constructing an efficient I LED display for low        and high resolution such that        -   a. I LED array chips containing one or a plurality of LED            emitter arranged.        -   b. LED emitters on a single chip are shared between            neighboring pixels of the display        -   c. I LED array chips are coupled to secondary optics to            direct and control light for the LED emitters in a            predetermined way in order to maximize the light directed to            the pixel display region.    -   2. The I LED array chips can be square, rectangular, triangular,        circular or a polygon shape.    -   3. The I LED array chips are configured I LED array chips are of        a single color R,G,B or any other color necessary.    -   4. In one embodiment, the ILED display is mounted on largely        transparent carrier such that the emitter light shines down        through the carrier    -   5. In one embodiment, the I LED display contains Light Guide        Panels which are machined into arrays of optically independent        pixels having inter-pixel gaps between the optically independent        pixels. The inter-pixel gaps are further filled with a        dielectric and/or reflective material to substantially reduced        optical crosstalk and enhance light collection efficiency,    -   6. As 1 where the secondary optics are integrated with ILED        array chip.    -   7. As 1 where the secondary optics are integrated with Light        Guide Panels.    -   8. As 1 where the secondary optics are on a panel or additional        sheet that is integrated into the system design.

In one embodiment, the ILED display is mounted in a flip-chipconfiguration such that the light shines away from the carrier.

1. A display device, comprising: a first inorganic light emitting diode(ILED) chip including a first ILED emitter, the first ILED emitterincluding an area of ILED emitter material configured to emit firstlight; and a lightguide configured to receive the first light from thefirst ILED emitter and output the first light at a light emission regionof the lightguide, the light emission region defining a surface of apixel of the display device, an area of the light emission region beinglarger than the area of ILED emitter material of the first ILED emitter.2. The display device of claim 1, further comprising a second ILED chipincluding a second ILED emitter configured to emit second light, andwherein the lightguide is configured to receive the second light fromthe second ILED emitter and output the second light at the lightemission region of the lightguide.
 3. The display device of claim 2,wherein a first subpixel of the pixel uses the first light from thefirst ILED emitter and a second subpixel of the pixel uses the secondlight from the second ILED emitter.
 4. The display device of claim 2,further comprising a third ILED chip including a third ILED emitterconfigured to emit third light, and wherein the lightguide is configuredto receive the third light from the third ILED emitter and output thethird light at the light emission region of the lightguide.
 5. Thedisplay device of claim 4, wherein the first light is red light, thesecond light is green light, and the third light is blue light.
 6. Thedisplay device of claim 1, wherein the lightguide comprises: a firstside including an input region to receive the first light; and a secondside opposite the first side, the second side including the lightemission region.
 7. The display device of claim 6, wherein thelightguide further comprises reflector optics configured to reflect thefirst light coupled into the lightguide at the input region.
 8. Thedisplay device of claim 7, wherein the reflector optics includes acorner reflector positioned in a corner of the lightguide at anintersection of the second side and a third side of the lightguidebetween the first and second sides.
 9. The display of claim 6, whereinthe lightguide further comprises a backreflector layer positioned alongthe second side of the lightguide to reflect the first light internallywithin the lightguide before emitting through the light emission region.10. The display of claim 1, wherein the lightguide further compriseslight extraction features at the light emission region, the lightextraction features reducing internal reflection of the first light atthe light emission region.
 11. The display device of claim 10, whereinthe light extraction features include ridged features.
 12. The displaydevice of claim 10, wherein the light extraction features are etchedinto a surface of the lightguide or mounted onto the surface of thelightguide.
 13. The display device of claim 1, wherein the first ILEDchip comprises a second ILED emitter.
 14. The display device of claim13, wherein the first and second ILED emitters of the first ILED chipemit light having the same color.
 15. The display device of claim 1,wherein the first ILED chip is embedded in the lightguide.
 16. Thedisplay device of claim 1, wherein the lightguide controlsdirectionality of the first light outputted at the light emissionregion.
 17. A display device, comprising: inorganic light emitting diode(ILED) chips, each ILED chip including ILED emitters; and a lightguideincluding lightguide portions separated by interpixel gaps, eachlightguide portion configured to receive light from adjacent ILEDemitters of different ILED chips and output the light at a lightemission region of the lightguide portion, the light emission region ofeach lightguide portion defining a surface of a pixel of the displaydevice, the ILED emitters of each ILED chip provide light to differentlightguide portions.
 18. The display device of claim 17, wherein theadjacent ILED emitters that emit light into each of the lightguideportions include a first ILED emitter that emits a first color light anda second ILED emitter that emits a second color light different from thefirst color light.
 19. The display device of claim 17, wherein: eachILED emitter of each ILED chip includes an area of ILED emittermaterial; and an area of the light emission region of each lightguideportion is larger than the area of ILED emitter material of the adjacentILED emitters that emit light into the lightguide portion.
 20. Thedisplay device of claim 19, wherein: each of the lightguide portionscontrol directionality of the light output at the light emission region;and the interpixel gaps reduce interpixel crosstalk between the ILEDemitters of each ILED chip.